JP3657396B2 - Key management system, key management apparatus, information encryption apparatus, information decryption apparatus, and storage medium storing program - Google Patents

Abstract

A key managing system including information transmitting apparatus which transmits a date and time when secrecy protection is ended to a key controlling apparatus. The key controlling apparatus searches a key control table for an encryption key associated with a decryption key and the date and time. The key controlling apparatus transmits an encryption key from the search to the information transmitting apparatus. The key controlling apparatus discloses a decryption key for the present date and time to an information receiving apparatus in response to a request for a decryption key. The information transmitting apparatus, upon receipt of the encryption key, encrypts information using the encryption key and transmits the encrypted information to the information receiving apparatus. The information receiving apparatus, for the present date and time matching with the date and time, acquires a disclosed decryption key and decrypts the encrypted information by using the decryption key.

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a system for managing a decryption key for decrypting encrypted data, and more particularly to a system suitable for realizing simultaneous disclosure of information to a plurality of users on a communication network.
[0002]
[Prior art]
In recent years, information has been actively exchanged between a plurality of terminals via a communication network such as the Internet.
[0003]
By the way, some information exchanged via a communication network must be kept secret before a certain date and time but may be disclosed thereafter. For example, confidential government information. Also, it must be ensured that information is disclosed to multiple users at the same time (in other words, multiple users can know the contents of information at the same time). There are also things. For example, information on commercial transactions such as bidding.
[0004]
For such information, conventionally, the created information is held at the terminal of the information creator until the date or date when the confidentiality of the information is released. A method of releasing or distributing to a plurality of users is used for the first time when the time limit has expired.
[0005]
[Problems to be solved by the invention]
However, in the above method, the information creator can simultaneously send information to a plurality of users when the amount of information to be disclosed or distributed is enormous or the number of users to be distributed is large. It is not easy to disclose reliably.
[0006]
In addition, the information creator must manage the disclosure date or distribution date of the information. In particular, when multiple types of information are disclosed or distributed, it is difficult to guarantee the disclosure or distribution of information to multiple users at the same time when such information is disclosed or distributed. is there.
[0007]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a system suitable for realizing simultaneous disclosure of information to a plurality of users.
[0008]
[Means for Solving the Problems]
The present invention solves the above-mentioned problems by using a key encryption method that is a technique for ensuring the security of information transmitted over a network.
[0009]
Specifically, the information encryption device that encrypts information using the encryption key, the information decryption device that decrypts information using the decryption key, and the information encryption device and the information decryption device are used. A key management system comprising a key management device for managing an encryption key and a decryption key, wherein at least the information encryption device and the key management device are connected by a communication network,
The key management device includes:
Key storage means for storing at least one pair of encryption key and decryption key;
A management table storage means for storing a management table indicating a correspondence relationship between the decryption key stored in the storage means and the release date or release date of the decryption key;
A key search means for searching for an encryption key paired with a decryption key corresponding to the date or date and time requested by the information encryption device by referring to the management table stored in the management table storage means;
An encryption key transmitting means for transmitting the encryption key searched by the search means to the information encryption apparatus via a communication network;
According to a management table stored in the management table storage means, and a decryption key release means for releasing a decryption key corresponding to the current date or date and time,
The information encryption device includes:
Date / time information transmitting means for transmitting date / time information on the date or date / time when the confidentiality of the information to be encrypted is released to the key management device via a communication network;
An encryption key receiving means for receiving an encryption key corresponding to the date or date specified by the date and time information sent from the key management device via the communication network and sent by the date and time information sending means;
An encryption means for encrypting information using the encryption key received by the encryption key receiving means;
Providing the date and time information about the information to the information encrypted by the encryption means, and creating encrypted information to be distributed to the information decryption device, and encryption information creation means,
The information decoding device includes:
Encrypted information acquisition means for acquiring encrypted information created by the information encryption device;
A decryption key acquisition means for acquiring a decryption key published by the key management device when the date or the date specified by the date information given to the encryption information acquired by the encryption information acquisition means is reached; ,
Decryption means for decrypting the encrypted information obtained by the encrypted information obtaining means using the decryption key obtained by the decryption key obtaining means.
[0010]
Here, the encryption key and the decryption key are, for example, a public key and a secret key in a public key cryptosystem.
[0011]
According to the present invention, according to the above configuration, the information creator can encrypt the created information and distribute it to the user before the date or date when the confidentiality of the information is released. Therefore, the information creator need not manage the date and time when the created information is disclosed.
[0012]
Further, the information user cannot acquire a decryption key for decrypting the received information until the date or date when the confidentiality of the received encrypted information is released. Therefore, information can be kept confidential until that date or date.
[0013]
Furthermore, the user of information can obtain a decryption key for decrypting the information after the date or date when the confidentiality of the received information is released. Accordingly, by decrypting the encrypted information received in advance using the decryption key, it is possible to guarantee the simultaneity of information disclosure to a plurality of users.
[0014]
In the present invention, when there are a plurality of the information decryption devices, each of the plurality of information decryption devices and the key management device are connected via a communication network, and the decryption key disclosure unit of the key management device includes: A broadcast key or a multicast packet destined for the plurality of information decryption apparatuses may be broadcast simultaneously to the plurality of information decryption apparatuses via a communication network. Alternatively, without connecting each of the plurality of information decryption devices and the key management device via a communication network, the decryption key disclosure unit of the key management device uses the wireless broadcast, so that the plurality of information The decryption key may be disclosed to the decryption device.
[0015]
In the present invention, when the key management device does not have a decryption key corresponding to the date or date requested by the information encryption device in the management table stored in the management table storage means, A key generation unit that generates an encryption key and a decryption key, and a management that associates the date or date requested by the information encryption device with the encryption key and the decryption key generated by the key generation unit and adds them to the management table And a table creation means.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described.
[0017]
FIG. 1 is a diagram showing an overall configuration of a key management system to which the present embodiment is applied.
[0018]
Here, reference numeral 50 denotes a key management apparatus, reference numeral 60 denotes an information transmission apparatus, and reference numeral 70 denotes an information reception apparatus. These devices are connected to each other via a communication network 90 such as a LAN.
[0019]
Here, one information transmitting device 60 and one information receiving device 70 are shown, but the present invention is not limited to this, and there may be a plurality of each.
[0020]
The devices 50, 60, and 70 shown in FIG. 1 can be realized by using an information processing device having a communication function, for example, a personal computer.
[0021]
The key management device 50 has a function of managing an encryption key used for information encryption processing and a decryption key used for information decryption processing. In this function, the CPU 1a loads the encryption key / decryption key management program 21, the encryption key service program 22, the decryption key service program 23, and the decryption key distribution program loaded from the magnetic disk 5a onto the memory 2a via the disk controller 4a. 24 is executed. In FIG. 1, reference numeral 20 a denotes an operating system (OS), and reference numeral 3 a denotes a network controller for realizing communication via the network 90.
[0022]
In addition to the OS 20a, the encryption key / decryption key management program 21, the encryption key service program 22, the decryption key service program 23, and the decryption key distribution program 24, the magnetic disk 5a has at least one pair of encryption key and decryption key. It is remembered. The at least one set of encryption key and decryption key is stored in the key management table 100 in association with the date and time when the decryption key is disclosed.
[0023]
An example of the key management table 100 is shown in FIG. In this example, a plurality of sets of the encryption key 102 and the decryption key 103 stored in the magnetic disk 5 a are associated with the date and time 101 that is the release date and time of the decryption key 103.
[0024]
Here, the encryption key 102 and the decryption key 103 are a public key and a secret key in the public key cryptosystem. The public key and the secret key in the public key cryptosystem have a property that it is extremely difficult to obtain one from the other. Therefore, in the public key cryptosystem, the public key for encryption is disclosed without making it secret, and only the secret key for decryption is kept secret. In other words, anyone can encrypt information by obtaining a public key that is publicly available, but for decrypting information encrypted with the public key, a private key paired with the public key is used. The security of information transmitted over the network is ensured by allowing only those who own the network to do so.
[0025]
The public key and the secret key in the public key cryptosystem are realized by using a one-way function that is easy to obtain a result value from an initial value but extremely difficult to obtain an initial value from a result value. Here, a system called RSA (Rivest, Shamir, Adleman) which is widely used now will be briefly described.
[0026]
First, two large prime numbers p and q are prepared. A product pq of p and q is n. Next, Euler function of n
φ (n) = (p−1) (q−1)
Choose any number e that is relatively prime. And the reciprocal of e in the modulo group of φ (n)
ed = 1 mod φ (n)
A number d is obtained. Then, regarding plaintext M and ciphertext C,
C = (M ^e ) Mod n
M = (C ^d ) Mod n
Is proved to hold. Therefore, d can be a secret key and a set of e and n can be a public key. E112 and n122 in FIG. 2 correspond to e and n in the above formula.
[0027]
The public key encryption method is described in detail, for example, in “Research on Data Protection and Encryption, Supervised by Shin Ichimatsu, Nikkei Inc. (Showa 58)”.
[0028]
The information transmission device 60 has a function of encrypting information. This function is realized by the CPU 1b executing the encryption key acquisition program 31 and the file encryption program 32 loaded from the magnetic disk 5b onto the memory 2b via the disk controller 4b. In FIG. 1, reference numeral 20b denotes an OS, and reference numeral 3b denotes a network controller for realizing communication via the communication network 90.
[0029]
The information receiving device 70 has a function of decoding information. This function is realized by the CPU 1c executing the decryption key acquisition program 41 and the file decryption program 42 loaded from the magnetic disk 5c onto the memory 2c via the disk controller 4c. In FIG. 1, reference numeral 20 c denotes an OS, and reference numeral 3 c denotes a network controller for realizing communication via the communication network 90.
[0030]
The operation of the key management system configured as described above will be briefly described.
[0031]
First, the information transmission device 60 transmits information related to the date and time when the confidentiality of the information to be encrypted is released to the key management device 50 via the communication network 90.
[0032]
In response to this, the key management device 50 refers to the key management table 100 stored in the magnetic disk 5a, thereby obtaining an encryption key corresponding to the date and time specified by the information sent from the information transmission device 60. Search for. Then, the retrieved encryption key is transmitted to the information transmission device 60 via the communication network 90.
[0033]
Further, the key management device 50 sequentially reads and discloses the decryption keys corresponding to the current date and time in accordance with the key management table 100 stored in the magnetic disk 5a.
[0034]
The information transmission device 60 encrypts information to be transmitted to the information reception device 70 using the encryption key transmitted from the key management device 50. Then, information related to the date and time when the confidentiality of the information is released is added to the encrypted information (hereinafter also referred to as encrypted information), and the information is transmitted to the information receiving device 60 via the communication network 90.
[0035]
In response to this, the information receiving apparatus 70 waits until the current date and time becomes the date and time specified by the information related to the date and time given to the encrypted information sent from the information transmitting device 60, and has reached the date and time. Sometimes, the decryption key published by the key management device 50 is acquired. Then, the encrypted information sent from the information transmitting device 60 is decrypted with the obtained decryption key.
[0036]
Next, details of each device constituting the system of the present embodiment will be described.
[0037]
First, details of the key management device 50 will be described.
[0038]
First, an operation when the CPU 1a executes the encryption / decryption key management program 21 loaded on the memory 2a in the key management device 50 will be described.
[0039]
FIG. 3 is a flowchart for explaining the operation when the CPU 1a executes the encryption key / decryption key management program 21 loaded on the memory 2a in the key management device 50.
[0040]
First, the start date / time, end date / time, and time interval, which are information for specifying the key to be added to the key management table 100, are displayed to the operator of the key management device 50 using a display device (not shown). Prompt for input. In response, in steps 601 to 603, the start date / time, end date / time, and time interval input to an input device (not shown) are received.
[0041]
In step 604, an encryption key / decryption key generation routine is called to generate a set of encryption key (e, n) and decryption key (d). The encryption key / decryption key generation routine will be described later.
[0042]
In step 605, the date and time are added to the key management table 100. Here, the date / time is calculated in step 609 to be described later in the flow shown in FIG. 3 when the process at step 605 is the first time, the start date and time accepted at step 601. Date and time.
[0043]
In step 606, the encryption key (e, n) generated in step 604 is added to the column corresponding to the date and time added to the key management table 100 in step 605 of the key management table 100.
[0044]
In step 607, the decryption key (d) generated in step 604 is added to the column corresponding to the date and time added to the key management table 100 in step 605 of the key management table 100.
[0045]
In step 608, it is determined whether or not the date and time added to the key management table 100 in step 605 is a date and time after the end date and time accepted in step 602. If the date and time after the end date and time are not reached, the process proceeds to step 609, and the date and time interval received in step 603 is added to the date and time added to the key management table 100 in step 605, and the obtained result is newly set. Set to the correct date and time.
[0046]
On the other hand, if the date is after the end date, this flow ends.
[0047]
By executing the encryption key / decryption key management program 21, the CPU 1a executes the encryption key / decryption key management program 21 to associate the public key and the decryption key with the date and time when the decryption key is made public as shown in FIG. A management table 100 can be created.
[0048]
Next, the process (encryption key / decryption key generation routine) at step 604 of the flow shown in FIG. 3 will be described.
[0049]
FIG. 4 is a flowchart for explaining the operation when the CPU 1a executes the encryption key / decryption key generation routine 700 in the encryption key / decryption key management program 21 loaded on the memory 2a in the key management device 50. FIG.
[0050]
First, two large prime numbers p and q are generated (step 701), and then a product n (= pq) of the generated p and q is generated (step 702).
[0051]
Next, the Euler function of this product n
φ (n) = (p−1) (q−1)
, Select any number e that is relatively prime (step 703). And the reciprocal of e in the modulo group of φ (n)
ed = 1 mod φ (n)
A number d is obtained (step 704). Next, e, n, and d obtained in steps 702 to 704 are set as return values (step 705), and then the process returns to the caller (step 799).
[0052]
Next, in the key management apparatus 50, an operation when the CPU 1a executes the encryption key service program 22 loaded on the memory 2a will be described.
[0053]
FIG. 5 is a flowchart for explaining the operation when the CPU 1a executes the encryption key service program 22 loaded on the memory 2a in the key management device 50. The encryption key service program 22 operates as a resident program of the key management device 50.
[0054]
First, it waits for an encryption key request to be sent via the communication network 90 (step 801). When the encryption key request is received, information on the date and time sent from the request source is acquired (step 802).
[0055]
Next, it is checked whether or not the date and time specified by the information acquired in step 802 exists in the key management table 100 stored in the magnetic disk 5a (step 803). If it does not exist, the encryption key / decryption key management program 21 is called, and the date and time specified by the information acquired in step 802 is set as the start date and time and end date and time received in steps 601 and 602 in FIG. The date and time interval received in 603 is set to an appropriate time, and the program is executed (step 804). As a result, the encryption key and public key associated with the date and time are added to the key management table 100. After completing the process in step 804, the process proceeds to step 805.
[0056]
On the other hand, if the date and time specified by the information acquired in step 802 exists in the key management table 100, the process proceeds to step 805 without executing step 804.
[0057]
In step 805, the encryption key associated with the date and time specified by the information acquired in step 802 is extracted from the key management table 100. Thereafter, the extracted encryption key is transmitted to the requester of the encryption key (step 806). After performing the above processing, the process returns to step 801 and again waits for an encryption key request to be sent via the communication network 90.
[0058]
Next, the operation when the CPU 1a executes the decryption key service program 23 loaded on the memory 2a in the key management device 50 will be described.
[0059]
FIG. 6 is a flowchart for explaining the operation when the CPU 1a executes the decryption key service program 23 loaded on the memory 2a in the key management device 50. The decryption key service program 23 operates as a resident program of the key management device 50.
[0060]
First, it waits for a decryption key request to be sent via the communication network 90 (step 901). When the decryption key request is received, information regarding the date and time sent from the request source is acquired (step 902).
[0061]
Next, it is checked whether or not the date and time specified by the information acquired in step 902 exists in the key management table 100 stored in the magnetic disk 5a (step 803). If it does not exist, an error code is transmitted to the requester of the decryption key (step 906), and then the process returns to step 901 to wait for the decryption key request to be sent again via the communication network 90.
[0062]
On the other hand, if the date and time specified by the information acquired in step 902 exists in the key management table 100, the decryption key associated with the date and time is extracted (step 904), and the extracted decryption key is used as the decryption key request source. (Step 905). Thereafter, the process returns to step 901 and waits again for a decryption key request to be sent via the communication network 90.
[0063]
Next, in the key management device 50, the operation when the CPU 1a executes the decryption key distribution program 24 loaded on the memory 2a will be described.
[0064]
FIG. 7 is a flowchart for explaining the operation in the key management device 50 when the CPU 1a executes the decryption key distribution program 24 loaded on the memory 2a. The decryption key distribution program 24 operates as a resident program of the key management device 50.
[0065]
First, the current date and time is acquired using the function of the OS 20a (step 1001), and then the decryption key associated with the acquired current date and time is extracted from the key management table 100 (step 1002).
[0066]
Next, the key management table 100 is searched for the date and time next to the date and time acquired in step 1001 (step 1003). Then, it is determined whether or not the current date and time acquired using the function of the OS 20a is after the next date and time searched in Step 1003 (Step 1004).
[0067]
If it is not after the next date and time, the information receiving device 70 (if there are a plurality of information transmitting devices 70) together with the information related to the date and time associated with the decryption key, the decryption key acquired in step 1002 On the other hand, simultaneous broadcast communication is performed via the communication network 90 (step 1005). Broadcast communication can be realized by using a broadcast packet or a multicast packet used in a communication system using a communication network. Here, the broadcast packet is obtained by adding each of a plurality of destination addresses to the header of the packet. A multicast packet is obtained by adding one address indicating a plurality of destinations to a packet header.
[0068]
After the processing in step 1005 is completed, the current date and time is acquired using the function of the OS 20a (step 1006), and the process returns to step 1004.
[0069]
On the other hand, if it is after the next date and time in step 1004, the process returns to step 1002.
[0070]
According to the above flow, each of the plurality of decryption keys stored in the key management table 100 is repeatedly broadcast from the date associated with itself to the date associated with the next decryption key to be disclosed. Is done. Here, an example of the history of the decryption key sent from the key management device 50 by the above flow is shown in FIG.
[0071]
Next, details of the information transmission device 60 will be described.
[0072]
Initially, the structure of the encryption information produced | generated by the information transmitter 60 is demonstrated.
[0073]
FIG. 9 is a diagram for explaining a configuration example of the encrypted information generated by the information transmitting apparatus 60. The information to be encrypted may be any data as long as it is electronic data such as a database or e-mail. Here, an example in which the information is encrypted in units of files is shown.
[0074]
In FIG. 9, reference numeral 202 denotes an encrypted text file. The ciphertext file 202 includes ciphertext data 204 that is data obtained by encrypting a plaintext file, and a header 205 added to the ciphertext data 204.
[0075]
The header 205 includes a decryption permission date 206 that is information indicating a date when decryption is possible (that is, a date when confidentiality is released), a file name 207 of the plaintext file that is the source of the ciphertext data 204, The file size 208 of the plaintext file and double data that is double-encrypted using the encryption key acquired from the key management device 50 and the individual encryption key described later, and the data key used for encryption of the plaintext file. And an encrypted data key 209.
[0076]
As can be seen from the configuration example of the encryption information shown in FIG. 9, in the present embodiment, the plaintext file is not directly encrypted using the encryption key acquired from the key management device 50, but is used in the symmetric key encryption method. The plaintext file is encrypted using a key to be used, that is, a data key that is commonly used for both encryption and decryption. The encryption key acquired from the key management device 50 is used to encrypt the data key used for encrypting the plain text file.
[0077]
Next, in the information transmitting apparatus 60, an operation when the CPU 1b executes the file encryption program 32 loaded on the memory 2b will be described.
[0078]
FIG. 10 is a flowchart for explaining the operation when the CPU 1b executes the file encryption program 32 loaded on the memory 2b in the information transmitting apparatus 60.
[0079]
First, using a display device (not shown), the user of the information transmission device 60 is urged to input a plaintext file name to be encrypted and a decryption permission date / time of the file. In response to this, in steps 1101 and 1102, the file name input to the input device (not shown) and the decryption permission date and time are received.
[0080]
Next, in step 1103, the file specified by the file name accepted in step 1101 is opened. Thereafter, a temporary file with a temporary name is created (step 1104).
[0081]
Next, in step 1105, a random number that is a data key is generated. Thereafter, the encryption key acquisition program 31 is executed to acquire from the key management device 50 the encryption key paired with the decryption key disclosed at the decryption permission date and time accepted in step 1102 (step 1106).
[0082]
In step 1107, the data key generated in step 1105 is encrypted using the encryption key acquired from the key management apparatus 50 in step 1106, thereby generating an encrypted data key. Thereafter, using a display device (not shown) or the like, an individual encryption key that is a key for double-encrypting the encrypted data key generated in step 1107 is input to the user of the information transmission device 60. Encourage you to. In response, in step 1108, an individual encryption key input to an input device (not shown) is accepted.
[0083]
Next, in step 1109, the encrypted data key generated in step 1107 is encrypted using the individual encryption key received in step 1108 to generate a double encrypted data key.
[0084]
In step 1110, a header is added to the beginning of the temporary file created in step 1104. Then, in the added header, information specifying the decryption permission date / time received in step 1102, the file name received in step 1101, the size of the file specified by this file name, and the double encrypted data generated in step 1109 The keys are written in this order (step 1111).
[0085]
Next, in step 1112, data is read from the plain text file opened in step 1103. Then, the read data is encrypted using the double encrypted data key generated in step 1109 to generate encrypted data (step 1113), and then this encrypted data is written in the temporary file created in step 1104. (Step 1114).
[0086]
In step 1115, it is determined whether or not encryption of all data in the plaintext file opened in step 1103 has been completed. If not completed, the above steps 1112 to 1114 are repeatedly executed until the process is completed. Then, after encryption of all the data in the plaintext file is completed, both the plaintext file and the temporary file are closed.
[0087]
In step 1117, it is determined whether or not the file name of the plain text file received in step 1101 is the same as the temporary name of the temporary file created in step 1104. If they are the same, the plain text file is deleted (step 1118), and then the file name of the temporary file is changed to the file name of the plain text file accepted in step 1101. Then, this flow ends.
[0088]
On the other hand, if they are not the same, the file name of the temporary file created in step 1104 is changed to the file name of the plain text file accepted in step 1101, and this flow ends.
[0089]
The information transmission device 60 can transmit the ciphertext file created as described above to a desired information reception device 70 via the communication network 90.
[0090]
Next, in the information transmitting apparatus 60, an operation when the CPU 1b executes the encryption key acquisition program 31 loaded on the memory 2b will be described.
[0091]
FIG. 11 is a flowchart for explaining the operation when the CPU 1b executes the encryption key acquisition program 31 loaded on the memory 2b in the information transmitting apparatus 60. This flow is executed by performing step 1106 of the flow shown in FIG.
[0092]
First, in step 1301, the information transmission device 60 is connected to the key management device 50 via the communication network 90.
[0093]
Next, in step 1302, information specifying the decryption permission date / time received in step 1102 of the flow shown in FIG. 10 is transmitted to the key management device 50. In response to this, the key management device 50 uses the encryption key service program 22 to search the key management table 100 for a decryption key associated with the decryption permission date and time, and to identify the decryption key and the decryption permission date and time. Is transmitted to the information transmitting device 60 that has transmitted.
[0094]
In step 1303, the encryption key associated with the decryption permission date and time transmitted from the key management device 50 to the key management device in step 1302 is received. Next, the connection with the key management device 50 is released (step 1304), and then the encryption key received in step 1303 is set as a return value (step 1305), and this flow is ended.
[0095]
Next, details of the information receiving apparatus 70 will be described.
[0096]
First, the operation when the CPU 1c executes the file decryption program 42 loaded on the memory 2c in the information receiving apparatus 70 will be described.
[0097]
FIG. 12 is a flowchart for explaining the operation when the CPU 1c executes the file decryption program 42 loaded on the memory 2c in the information receiving apparatus 70.
[0098]
First, the name of the ciphertext file to be decrypted among the ciphertext files sent from the information transmitting device 60 is input to the user of the information receiving device 70 using a display device not shown. Encourage you to. In response, in step 1201, a file name input to an input device (not shown) is received.
[0099]
Next, in step 1202, the ciphertext file specified by the file name accepted in step 1201 is opened, and then the double encrypted data key is extracted from the header of this ciphertext file (step 1203). Thereafter, using a display device (not shown), the user of the information receiving device 60 is prompted to input an individual encryption key used for decrypting the extracted double encrypted data key. In response, in step 1204, an individual encryption key input to an input device (not shown) is received.
[0100]
The individual encryption key is assumed to be known in advance from the sender of the ciphertext file.
[0101]
Next, in Step 1205, the double encrypted data key extracted in Step 1203 is converted into a single encrypted data key using the individual encryption key received in Step 1204.
[0102]
In step 1206, information on the decryption permission date and time is extracted from the header of the ciphertext file opened in step 1203. Thereafter, the decryption key acquisition program 41 is executed using the date and time specified by this information as an argument (step 1207). Thereby, the decryption key associated with the decryption permission date and time is acquired from the key management device 50.
[0103]
Next, in step 1208, it is determined whether acquisition of the decryption key is successful by referring to the return value from the decryption key acquisition program 41 executed in step 1207. If acquisition is not successful, the ciphertext file opened in step 1202 is closed (step 1289), and this flow is terminated.
[0104]
On the other hand, if acquisition of the decryption key is successful, the process proceeds to step 1209.
[0105]
In step 1209, the single encrypted data key obtained in step 1205 is decrypted using the decryption key obtained in step 1207, thereby obtaining the data key used for encrypting the ciphertext file.
[0106]
Next, in step 1210, a temporary file with a temporary name is created. Thereafter, the cipher data is read from the ciphertext file opened in step 1202 (step 1211). Then, the read encrypted data is decrypted using the data key generated in step 1209 to generate plaintext data (step 1212), and then this plaintext data is written to the temporary file created in step 1210 (step 1213). ).
[0107]
In step 1214, it is determined whether or not the decryption of all the cipher data in the ciphertext file opened in step 1202 has been completed. If not completed, the above steps 1211 to 1213 are repeatedly executed until the process is completed. Then, after the decryption of all the encrypted data in the ciphertext file is completed, both the ciphertext file and the temporary file are closed.
[0108]
In step 1216, it is determined whether or not the file name of the ciphertext file received in step 1201 is the same as the temporary name of the temporary file created in step 1210. If they are the same, the ciphertext file is deleted (step 12176), and then the file name of the temporary file is changed to the file name of the ciphertext file accepted in step 1201. Then, this flow ends.
[0109]
On the other hand, if they are not the same, the file name of the temporary file created in step 1210 is changed to the file name of the ciphertext file accepted in step 1201, and this flow ends.
[0110]
Next, in the information receiving apparatus 70, an operation when the CPU 1c executes the decryption key acquisition program 41 loaded on the memory 2c will be described.
[0111]
FIG. 13 is a flowchart for explaining the operation when the CPU 1c executes the decryption key acquisition program 41 loaded on the memory 2c in the information receiving apparatus 70. This flow is executed by performing step 1207 of the flow shown in FIG.
[0112]
First, in step 1401, the current date and time is acquired using the function of the OS 20c. Next, the acquired current date and time are compared with the decryption permission date and time received as an argument (step 1402). As a result, if the current date and time is after the decryption permission date and time, the process proceeds to step 1406. If the current date and time is earlier than the decryption permission date and time, the process proceeds to step 1403.
[0113]
In step 1403, a display device (not shown) is used to inquire the user of the information receiving device 70 whether or not to wait until the current date and time becomes the decoding permission date and time. And it waits for a user to input an instruction into an input device (not shown).
[0114]
If the input user instruction indicates not to wait until the current date and time becomes the decoding permission date and time, the error code is set as a return value (step 1489), and then this flow ends.
[0115]
On the other hand, if the input user instruction indicates that the current date and time will wait until the decryption permission date and time is reached, the current date and time is acquired using the function of the OS 20c (step 1404). The current date and time are compared with the decryption permission date and time received as an argument (step 1405). The processing in step 1404 and step 1405 is repeatedly executed until the acquired current date is after the decryption permission date received as an argument.
[0116]
In step 1406, the key management device 50 receives the decryption key released (flowing on the communication network 90), and whether there is a decryption key associated with the decryption permission date and time received as an argument. Determine whether or not. This determination is made based on information related to the date and time added to the received decryption key.
[0117]
If there is a decryption key associated with the decryption permission date and time received as an argument, this decryption key is set as a return value (step 1479), and this flow ends. On the other hand, if there is no decryption key associated with the decryption permission date and time received as an argument, the process proceeds to step 1408.
[0118]
In step 1408, the information receiving device 70 is connected to the key management device 50 via the communication network 90.
[0119]
Next, in step 1409, information specifying the decryption permission date and time received as an argument is transmitted to the key management device 50. In response to this, the key management device 50 uses the decryption key service program 23 to search the key management table 100 for a decryption key associated with the decryption permission date and time, and to identify the decryption key and the decryption permission date and time. Is transmitted to the information receiving apparatus 70 that has transmitted.
[0120]
In step 1410, the decryption key sent from the key management device 50 and associated with the decryption permission date / time is received. Thereafter, the connection with the key management device 50 is released (step 1411). Next, the reception result of the decryption key is checked to determine whether or not the decryption key can be acquired without error (step 1412).
[0121]
If it can be acquired without error, this acquired decryption key is set as a return value (step 1479), and this flow is terminated. On the other hand, if there is an error and acquisition fails, the error code is set as a return value (step 1489), and then this flow ends.
[0122]
In the key management system of the present embodiment described above, the user of the information transmission device 60 encrypts the created information and distributes the information to the user before the date when the confidentiality of the information is released. Can do. Therefore, it is not necessary to manage the disclosure date and time of the created information.
[0123]
Further, the user of the information receiving apparatus 70 cannot obtain a decryption key for decrypting the received information until the date and time when the confidentiality of the received encrypted information is released. Therefore, information can be kept confidential until that date or date.
[0124]
Furthermore, the user of the information receiving apparatus 70 can obtain a decryption key for decrypting the received information after the date or date when the confidentiality of the received information is released. Therefore, by decrypting the encrypted information received in advance using the decryption key, it is possible to guarantee the simultaneity of information disclosure for the users of the plurality of information receiving apparatuses 70.
[0125]
In the above embodiment, the description has been given of the case where the key management device 50 discloses the decryption key (broadcast communication) using one channel as shown in FIG. However, the present invention is not limited to this. For example, as shown in FIG. 14, the decryption key may be disclosed using a plurality of channels. In this case, the period for disclosing the same decryption key (broadcast communication) can be extended. As a result, the information receiving device 70 can acquire the decryption key corresponding to the decryption permission date and time without accessing the key management device 50 even after a while after the decryption permission date and time is reached.
[0126]
In the above-described embodiment, the key management device 50 has been described in which the key is disclosed using a broadcast packet or a multicast packet using the communication network 90. However, the present invention is not limited to this. The disclosure of the decryption key can also be realized by wireless broadcasting using a satellite as shown in FIG. By using wireless broadcasting such as satellites, it becomes possible to distribute the decryption key to all of the plurality of information receiving apparatuses 70 at the same time.
[0127]
Further, in the above-described embodiment, the case where the data key is encrypted with the individual encryption key has been described. However, the encryption key and the decryption key acquired from the key management device 50 may be directly used for data encryption and decryption. Is possible. However, in this case, it should be noted that all the encrypted data having the same decryption permission date and time can be decrypted with the decryption key associated with the decryption permission date and time.
[0128]
In addition, in the above-described embodiment, the information transmitted by the information transmitting device 60 is transmitted to the information receiving device 70 via the communication network. However, the distribution of the encrypted information is performed using the communication network. For example, the recording may be performed on a storage medium such as a floppy disk or a CD-ROM. In the above-described embodiment, the case where the management and service of the encryption key and the decryption key are performed using a single key tube device 50 has been described. However, these processes are shared among a plurality of information processing devices. You may do it.
[0129]
Further, in the above-described embodiment, the description has been given of the case where various programs executed by the respective devices constituting the key management system are stored on the magnetic disk. However, the present invention is not limited to this, and may be stored in, for example, an optical disc such as a CD-ROM or other recording medium.
[0130]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a system suitable for realizing simultaneous disclosure of information to a plurality of users.
[Brief description of the drawings]
FIG. 1 is a diagram showing an overall configuration of a key management system to which an embodiment of the present invention is applied.
FIG. 2 is a diagram showing an example of a key management table 100 stored on the magnetic disk 5a of the key management device 50. FIG.
FIG. 3 is a flowchart for explaining the operation when the CPU 1a executes the encryption / decryption key management program 21 loaded on the memory 2a in the key management device 50.
It is a figure which shows the example of 1 structure of the encryption key management system in the Example of this invention.
FIG. 4 is a flowchart for explaining an operation in the key management device 50 when the CPU 1a executes an encryption key / decryption key generation routine 700 in the encryption key / decryption key management program 21 loaded on the memory 2a. FIG.
FIG. 5 is a flowchart for explaining an operation when the CPU 1a executes the encryption key service program 22 loaded on the memory 2a in the key management device 50.
FIG. 6 is a flowchart for explaining an operation when the CPU 1a executes the decryption key service program 23 loaded on the memory 2a in the key management device 50.
FIG. 7 is a flowchart for explaining the operation when the CPU 1a executes the decryption key distribution program 24 loaded on the memory 2a in the key management device 50.
8 is a diagram showing an example of a history of decryption keys sent from the key management device 50 by the flow shown in FIG.
FIG. 9 is a diagram for explaining a configuration example of encrypted information generated by the information transmitting apparatus 60;
FIG. 10 is a flowchart for explaining the operation when the CPU 1b executes the file encryption program 32 loaded on the memory 2b in the information transmitting apparatus 60.
FIG. 11 is a flowchart for explaining the operation when the CPU 1b executes the encryption key acquisition program 31 loaded on the memory 2b in the information transmitting apparatus 60.
12 is a flowchart for explaining the operation when the CPU 1c executes the file decryption program 42 loaded on the memory 2c in the information receiving apparatus 70. FIG.
FIG. 13 is a flowchart for explaining the operation when the CPU 1c executes the decryption key acquisition program 41 loaded on the memory 2c in the information receiving apparatus 70.
FIG. 14 is a diagram for explaining a modification of the embodiment of the present invention, and shows the decryption key sent from the key management device 50 when the decryption key is distributed using a plurality of channels. It is a figure which shows an example of a log | history.
FIG. 15 is a diagram for explaining a modification of the embodiment of the present invention, and is a diagram illustrating an example in which wireless broadcasting using a satellite or the like is used for distributing a decryption key.
[Explanation of symbols]
1a to 1c CPU
2a-2c memory
3a-3c network controller
4a-4c disk controller
5a-5c magnetic disk
20a-20c OS
21 Encryption key / decryption key management program
22 Cryptographic key service program
23 Decryption key service program
24 Decryption key distribution program
31 Encryption key acquisition program
32 File encryption program
41 Decryption key acquisition program
42 File decryption program
50 Key management device
60 Information transmitter
70 Information receiver

Claims (23)

An information encryption apparatus that encrypts information using an encryption key, an information decryption apparatus that decrypts information using a decryption key, and an encryption key and a decryption key used in the information encryption apparatus and the information decryption apparatus A key management system comprising: a key management device for managing
The key management device includes:
Management table storage means for storing a management table in which at least one pair of encryption key and decryption key is registered in association with the release date or release date of the decryption key;
A key search unit that searches the management table for an encryption key paired with a decryption key whose date or date indicated by the date and time information sent from the information encryption device is a public date or a public date and time;
An encryption key transmitting means for transmitting the encryption key searched by the key searching means to the information encryption device;
By referring to the management table, the decryption key is disclosed to specify the decryption key having the current date or date and time as the public date or the public date and time, and to disclose the decryption key,
The information encryption device includes:
Date / time information transmitting means for transmitting date / time information on the date or date / time when the confidentiality of the information to be encrypted is released to the key management device;
An encryption key receiving means for receiving the encryption key corresponding to the date or date and time disclosed by the date and time information sent by the date and time information sending means sent from the key management device;
An encryption means for encrypting the information to be encrypted using an encryption key received by the encryption key receiving means;
The encrypted information is created by adding date / time information on the date or date / time when the confidentiality of the information is released to the information encrypted by the encryption means, and the date indicated by the date / time information is the encrypted information. Or an encrypted information creating means for distributing to the information decryption device prior to the date and time ,
The information decoding device includes:
Encrypted information acquisition means for acquiring encrypted information distributed by the information encryption device;
Acquire from the key management device the decryption key disclosed by the key management device when the date or date specified by the date and time information given to the encrypted information acquired by the encryption information acquisition means is reached. Decryption key acquisition means for
A key management system comprising: a decryption unit that decrypts the encrypted information acquired by the encrypted information acquisition unit using the decryption key acquired by the decryption key acquisition unit. The key management system according to claim 1,
There are a plurality of the information decoding devices,
The decryption key disclosure unit of the key management device includes:
Key management characterized in that broadcast keys or multicast packets destined for the plurality of information decryption devices are used to broadcast a decryption key to the plurality of information decryption devices via a communication network. system. The key management system according to claim 1,
There are a plurality of the information decoding devices,
The decryption key disclosure unit of the key management device includes:
A key management system characterized in that a decryption key is disclosed to the plurality of information decryption devices by using wireless broadcasting. The key management system according to claim 1, 2, or 3,
The key management device includes:
When a decryption key whose date or date indicated by the date / time information sent from the information encryption device is not registered in the management table is newly registered as a set of encryption key and decryption key. A key generation means for generating;
A management table for adding a set of encryption key and decryption key newly generated by the key generation means to the management table by setting the date or date indicated by the date / time information to the date of disclosure or date / time of the decryption key And a creating means. The key management system according to claim 1, 2, 3 or 4,
In the information encryption apparatus,
The encryption means includes
The information to be encrypted is encrypted using a data key, and the data key is double-encrypted using the individual encryption key input by the operator and the encryption key received by the encryption key receiving means. Is,
The encrypted information creating means includes:
The information decrypted by adding to the information encrypted by the encryption means date / time information related to the date or date when the confidentiality of the information is released and a data key double-encrypted by the encryption means Encryption information to be distributed to the encryption device,
In the information decoding apparatus,
The decoding means includes
Double-encrypted data added to the encryption information acquired by the encryption information acquisition unit using the individual encryption key input by the operator and the decryption key acquired by the decryption key acquisition unit A key management system characterized in that the key is decrypted and the encrypted information is decrypted using the decrypted data key. The key management system according to claim 1, 2, 3, 4 or 5,
The information encryption device includes:
A key management system, further comprising: encrypted information transmitting means for transmitting the encrypted information created by the encrypted information creating means to the information decrypting apparatus via a communication network. A key management device that manages an encryption key used by the information encryption device for encryption of information and a decryption key used by the information decryption device for decryption of information ,
Management table storage means for storing a management table in which at least one pair of encryption key and decryption key is registered in association with the release date or release date of the decryption key;
A key search unit that searches the management table for an encryption key paired with a decryption key having the date or date indicated by the date and time information sent from the information encryption device for encrypting information as the release date or the release date and time;
Encrypted information is created using an encryption key, and the encryption key searched by the key search means is transmitted to the information encryption device distributed to the information decryption device prior to the date or date indicated by the date and time information An encryption key transmission means;
By referring to the management table, a decryption key having the current date or date as the release date or the release date is specified, and the decryption key is used to decrypt the encrypted information distributed by the information encryption device using the decryption key to decrypt the key management apparatus characterized by comprising a decryption key announcement means to expose at least one of the information decoding device. The key management device according to claim 7,
The decryption key disclosure means includes
A broadcast key or a multicast packet destined for the at least one information decryption device is used to broadcast the decryption key to the at least one information decryption device via a communication network. Key management device. The key management device according to claim 7,
The decryption key disclosure means includes
A key management device, wherein a decryption key is disclosed to the at least one information decryption device by using wireless broadcasting. The key management device according to claim 7, 8 or 9,
When a decryption key whose date or date indicated by the date / time information sent from the information encryption device is not registered in the management table is newly registered as a set of encryption key and decryption key. A key generation means for generating;
A management table for adding a set of encryption key and decryption key newly generated by the key generation means to the management table by setting the date or date indicated by the date / time information to the date of disclosure or date / time of the decryption key And a creating means. An information encryption device for encrypting information,
Encryption key acquisition means for acquiring from the key management device according to claim 7, 8, 9, or 10 an encryption key that is paired with a decryption key that is disclosed on the date or date when the confidentiality of the information to be encrypted is released;
An encryption means for encrypting the information to be encrypted using the encryption key acquired by the encryption key acquisition means;
The encrypted information is created by adding date / time information on the date or date / time when the confidentiality of the information is released to the information encrypted by the encryption means, and the date indicated by the date / time information is the encrypted information. or prior to the date and time that it comprises a, an encryption information generating means for distributing the information decoding device for performing decoding information encrypted and wherein the said information. The information encryption device according to claim 11,
The encryption means includes
The information to be encrypted is encrypted using a data key, and the data key is double-encrypted using the individual encryption key input by the operator and the encryption key received by the encryption key receiving means. Is,
The encrypted information creating means includes:
The information decrypted by adding to the information encrypted by the encryption means date / time information related to the date or date when the confidentiality of the information is released and a data key double-encrypted by the encryption means An information encryption device that creates encrypted information to be distributed to an encryption device. An information decoding device for decoding information,
Encrypted information acquisition means for acquiring encrypted information distributed by the information encryption device according to claim 11 prior to the date or date indicated by the date information given to the encrypted information;
Wherein when a date or date and time specified by the date information published by the key management apparatus according to claim 7, 8, 9 or 10, wherein a decryption key, the decryption key acquisition means for acquiring from the key management apparatus ,
An information decryption apparatus comprising: decryption means for decrypting the encrypted information using the decryption key acquired by the decryption key acquisition means. An information decoding device for decoding information,
Encrypted information acquisition means for acquiring the encrypted information distributed by the information encryption device according to claim 12 prior to the date or date indicated by the date information given to the encrypted information;
Decryption key acquisition means for acquiring a decryption key from the key management device disclosed by the key management device according to claim 7, 8, 9, or 10 when the date or date specified by the date information is reached ,
Decryption means for decrypting the encrypted information using the decryption key acquired by the decryption key acquisition means,
The decoding means includes
Using the individual encryption key input by the operator and the decryption key acquired by the decryption key acquisition means, the double-encrypted data key added to the encryption information is decrypted and the decryption An information decryption apparatus, wherein the encrypted information is decrypted using a data key that has been converted into a data. A storage medium storing an encryption key used by an information encryption device for encrypting information and a program for managing a decryption key used by the information decryption device for decrypting information ,
The program is stored in the information processing device.
A first process of storing at least one pair of encryption key and decryption key in a management table in association with the release date or release date of the decryption key;
A second process of searching the management table for an encryption key paired with a decryption key whose date or date indicated by the date / time information sent from the information encryption device is a publication date or a publication date;
The encryption key is created using the encryption key, and the encryption key retrieved in the second process is transmitted to the information encryption device that is distributed to the information decryption device prior to the date or date indicated by the date and time information. A third process to
By referring to the management table, a decryption key having the current date or date as the release date or the release date is specified, and the decryption key is used to decrypt the encrypted information distributed by the information encryption device using the decryption key storage medium storing a program, wherein the fourth process that exposes the information decoding device, is intended to run for decoding. A recording medium storing a program for encrypting information,
The program is stored in the information processing device.
A first process for obtaining an encryption key paired with a decryption key released on the date or date when the confidentiality of information to be encrypted is released from the key management device according to claim 7, 8, 9, or 10;
A second process for encrypting the information to be encrypted using the encryption key obtained in the first process;
The encrypted information is created by adding date / time information on the date or date / time when the confidentiality of the information is released to the information encrypted in the second processing, and the date / time information indicates the encrypted information. day or prior to the time, the storage medium storing the program, wherein the third process of distributing the information decoding device that performs decoding, is intended to the execution of the information. A storage medium storing a program for decrypting information,
The program is stored in the information processing device.
A first process for acquiring the encrypted information distributed by the information encryption device according to claim 11 prior to a date or a date indicated by the date / time information attached to the encrypted information ;
A second process for acquiring a decryption key from the key management device disclosed in the key management device according to claim 7, 8, 9, or 10 when the date or date specified by the date information is reached. ,
A third process for decrypting the encrypted information created by the information encryption device using the decryption key acquired in the second process; Storage medium. A key management method of a key management apparatus for managing an encryption key used by an information encryption apparatus for encrypting information and a decryption key used by an information decryption apparatus for decrypting information ,
The key management device includes:
At least one set of an encryption key and a decryption key, and Installing corresponding to publication date or publishing date and time of the decryption key, a first step of storing the management table,
A second step of searching the management table for an encryption key paired with a decryption key whose date or date indicated by the date / time information sent from the information encryption device is a release date or a release date ;
Third step of transmitting the retrieved encryption key to the information encryption device that distributes the encryption information created using the encryption key to the information decryption device prior to the date or date indicated by the date information. When,
By referring to the management table, a decryption key having the current date or date as the release date or the release date is specified, and the decryption key is used to decrypt the encrypted information distributed by the information encryption device using the decryption key to decrypt the key management method, which comprises carrying out the fourth step to expose at least one of the information decoding device. The key management method according to claim 18, comprising:
The third step includes
A key management method characterized in that a broadcast key or a multicast packet destined for the at least one information decryption device is broadcast simultaneously to the at least one information decryption device via a communication network. . The key management method according to claim 18, comprising:
The third step includes
A key management method characterized in that a decryption key is disclosed to the at least one information decryption apparatus by using wireless broadcasting. The key management method according to claim 18, 19 or 20,
The key management device includes:
When a decryption key whose date or date indicated by the date / time information sent from the information encryption device is not registered in the management table is newly registered as a set of encryption key and decryption key. A fifth step of generating,
A set of encryption key and decryption key newly generated in the fifth step is added to the management table by setting the date or date indicated by the date / time information to the date of disclosure or date / time of the decryption key. the key management method, characterized by further performing 6 and steps, a. An information encryption device for encrypting information using an encryption key, a plurality of information decryption devices for decrypting information using a decryption key, an encryption key used in the information encryption device and the information decryption device, and A key management system that manages a decryption key, and a method for simultaneously disclosing information of a key management system comprising :
The key management device registering at least one pair of encryption key and decryption key in a management table in association with the release date or release date of the decryption key ;
The information encryption apparatus encrypts information using an encryption key paired with a decryption key registered in the management table and having a release date or a release date as the release date or release date. and of the steps of distributing the respective information decoding device,
The key management device, by referring to the management table, identifying a decryption key whose current date or date is a disclosure date or disclosure date, and publishing the decryption key to each information decryption device ; ,
Each of the information decoding device, the simultaneous publishing information and performing the steps of: decoding using the decryption key information the information encrypting apparatus has encrypted the key management device published. A method for simultaneously publishing information according to claim 22,
Wherein the step of distributing includes the information encrypting apparatus, by applying a date and time information indicating the date or time sensitivity of the information to encrypted information is released, and distributed to each of the information decoding device,
In the decrypting step, each of the information decryption devices uses the decryption key disclosed when the information encrypted by the information encryption device is indicated by the date / time information attached to the information or when the date / time is reached. A method for simultaneously publishing information, characterized in that decryption is performed using.

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